The warning is that the Hahnel USB plug that fits into the Oly cameras was too big on my cable and it needed some gentle filing down to make it fit nicely. I told Hahnel about the problem and sent photos and they passed it on to engineering, and they sent me two spare cables, again they needed to be filed down a bit.

Evidently some other brand remotes have had the same problem, so if the plug is hard to push in, don't push any more but file it down to fit.

First the regular USB cable that comes with the camera, the 6.32mm figure can vary up to the obvious maximum of 6.35mm which is exactly 1/4 inch.

Olympus cable just right.

Now the Hahnel cable, too big and it jams and comes apart when trying to extract it, file the ends down until it measures 6.35mm or less or until it fits nicely.